1. Field of the Invention
Aspects of this invention relate to handheld electronic devices and user interfaces for such devices such as a thumbwheel switch and to methods of assembling the devices.
2. Background Information
Handheld electronic devices are in widespread use. Some utilize as part of user interface a thumbwheel switch that can be used to scroll through and make selections from actions or entries presented on a display. Typically, a portion of the thumbwheel protrudes from the side of the housing where it can be manipulated easily by the thumb as the device is held in the palm of the user's hand. The thumbwheel switch generates electrical signals that must be passed to circuits provided usually on a printed circuit board contained within the housing of the handheld electronic device. Some factors that need to be considered when providing thumbwheel switches in handheld electronic devices include: ease of use of the thumbwheel switch, the shrinking overall size of the handheld electronic devices, the accommodation of larger displays, and the trend toward automatic assembly.
A current handheld electronic device has a thumbwheel switch and other components that are mechanically secured to a printed circuit board and electrically connected to the circuits of the printed circuit board using surface mounting technology (SMT). In this process, solder is screen printed to form contact pads on the printed circuit board substrate. The components, including the thumbwheel switch, are pressed into the solder at the appropriate locations and the assembly is passed through an oven that melts the solder, which then cools to mechanically and electrically connect the thumbwheel switch and other components to the printed circuit board. However, the thumbwheel itself is mounted on a body of the thumbwheel switch which in turn is seated on the printed circuit board so that the wheel is offset considerably from the plane of the printed circuit board substrate. When the printed circuit board is installed in the housing in a plane generally parallel to the front surface of the housing of the handheld electronic device, the thumbwheel is positioned behind the printed circuit board well below the front of the device where it is less comfortable to operate. The thumbwheel switch cannot be positioned in front of the printed circuit board because of interference with the device's display, typically a liquid crystal display (LCD).
In another handheld electronic device, the thumbwheel switch is mounted on a separate board that allows it to be installed in the device with the axis of rotation of the wheel at an angle to the face of the device. While this is ergonomically more satisfactory, it has important disadvantages. First, it requires more depth in the housing, and therefore, it cannot overlap the display. This means that the overall width of the device must be greater and/or the display must be made narrower. Second, it makes the device more costly to assemble as separate electrical connections are required between the switch and the circuits of the printed circuit board and additional assembly steps that are more difficult to automate are needed to mount the switch and make the electrical connections.
One handheld electronic device moves the wheel of the thumbwheel switch into a cutout in the edge of the substrate of the printed circuit board so that it is in the plane of the substrate. However, the thumbwheel switch is secured to the printed circuit board by screws, thus requiring additional assembly steps. Furthermore, a ribbon connector is required to electrically connect the switch to the circuits of the printed circuit board. Again, this adds steps to the assembly process and requires additional space on the printed circuit board.
In summary, there is room for improvement in providing handheld electronic devices with thumbwheel switches.